class Compiler {
    constructor(vm) {
        this.el = vm.$el
        this.vm = vm
        this.compile(this.el)
    }
    //编译模板，处理文本节点和元素节点
    compile(el) {
        const childNodes = el.childNodes
        Array.from(childNodes).forEach(node => {
            //处理文本节点
            if (this.isTextNode(node)) {
                this.compileText(node)
            } else if (this.isElementNode(node)) {
                //处理元素节点
                this.compileElement(node)
            }

            //判断node节点是否有子节点，如果有子节点，要递归调用compile
            if (node.childNodes && node.childNodes.length) {
                this.compile(node)
            }
        })
    }
    //编译元素节点，处理指令
    compileElement(node) {
        console.log(node.attributes);
        //遍历所有的属性节点
        Array.from(node.attributes).forEach(attr => {
            //判断是否是指令
            let attrName = attr.name
            if (this.isDirective(attrName)) {
                //v-text => text
                attrName = attrName.substr(2)
                let key = attr.value
                this.update(node, key, attrName)
            }
        })
    }
    update(node, key, attrName) {
        // 指令名
        let orderName = ''
        // 事件名
        let eventName = ''
        // 处理事件绑定的冒号
        if (attrName.indexOf(':') !== -1) {
            [orderName, eventName] = attrName.split(':')
        }
        orderName = orderName || attrName
        const updaterFnc = this[`${orderName}Updater`]
        let value = eventName ? this.vm.$options.methods[key] : this.vm[key]
        updaterFnc && updaterFnc.call(this, node, value, key, eventName)
    }
    //处理v-text指令
    textUpdater(node, value, key) {
        node.textContent = value
        //创建watcher对象，当数据改变更新视图
        new Watcher(this.vm, key, (newValue) => {
            node.textContent = newValue
        })
    }
    //处理v-model指令
    modelUpdater(node, value, key) {
        node.value = value
        //创建watcher对象，当数据改变更新视图
        new Watcher(this.vm, key, (newValue) => {
            node.value = newValue
        })
        //双向绑定
        node.addEventListener('input', () => {
            this.vm[key] = node.value
        })
    }
    //处理v-html指令
    htmlUpdater(node, value, key) {
        node.innerHTML = value
        new Watcher(this.vm, key, (newValue) => {
            node.innerHTML = newValue
        })
    }
    //处理v-on指令
    onUpdater(node, value, key, eventName) {
        node.addEventListener(eventName, value)
        new Watcher(this.vm.$options.methods, key, (newValue) => {
            node.addEventListener(eventName, newValue)
        }, (oldVlaue) => {
            // 先把之前的事件处理函数卸载掉
            node.removeEventListener(eventName, oldVlaue)
        })
    }
    //编译文本节点，处理插值表达式
    compileText(node) {
        // console.dir(node);
        //{{ msg }}
        const reg = /\{\{(.+?)\}\}/
        const value = node.textContent
        if (reg.test(value)) {
            const key = RegExp.$1.trim()
            node.textContent = value.replace(reg, this.vm[key])
            //创建watcher对象，当数据改变更新视图
            new Watcher(this.vm, key, (newValue) => {
                node.textContent = newValue
            })
        }
    }
    //判断元素属性是否是指令
    isDirective(attrName) {
        return attrName.startsWith('v-')
    }
    //判断节点是否是文本节点
    isTextNode(node) {
        return node.nodeType === 3
    }
    //判断节点是否是元素节点
    isElementNode(node) {
        return node.nodeType === 1
    }
}